The present invention relates to a simplified loading device capable of applying a fixed load to a moving element such as a motor shaft without the occurrence of friction.
As is well known, a motor braking method has been used in which a sliding brake is incorporated in a motor casing for a motor, and this brake is always applied to provide braking torque at the time of stoppage.
FIG. 6 shows a simplified braking mechanism for a reversible motor, which has been used conventionally.
A motor casing 100 for a motor contains a stator 101 and a rotor 102, and a brake disc 104 is mounted on a rotating shaft 103 of the rotor 102. On the inside face of the motor casing 100 opposed to the brake disc 104 are disposed a plurality of brake shoes 105 which are in slidable contact with the brake disc 104. The brake shoe 105 is inserted in a hole 108 formed axially in a bearing housing portion 107 on which a bearing 106 for supporting the rotating shaft 103 is mounted, and is urged toward the brake disc 104 via a coil spring 109. Reference numeral 110 denotes a spring support plate.
This braking mechanism is configured so that the brake shoes 105 are always pressed on the brake disc 104 by the urging force of the coil spring 109 to bring the brake shoes 105 into contact with the brake disc 104, and thereby a load is developed due to friction, by which braking action and holding torque at the time of stoppage are obtained.
FIG. 7 shows a braking mechanism that obtains a load using a permanent magnet.
A rotating disc 112 mounted with a hysteresis material 111 along the circumferential direction on one side face in the axial direction. On the other hand, a yoke 114 provided with a permanent magnet 113 on a face opposed to the hysteresis material 111 is mounted on a bearing 106 supporting the rotating shaft 103. The relative rotation of the permanent magnet 113 and the hysteresis material 111 around the same axis develops a load due to magnetism.
However, according to the above-described braking mechanism using friction, the loading force is changed by the time change of surface condition of a shoe material used for the brake shoe 105, and the service life is limited by the wear of shoe material.
Also, in the above-described hysteresis brake, the loading force depends on magnetic lines passing through a gap between the permanent magnet 113 and the hysteresis material 111, so that the gap must be adjusted delicately, and also the expensive hysteresis material 111 must be used.
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a simplified loading device capable of generating a high and steady loading force and being made smaller in size as compared with the related art.
To achieve the above object, the present invention provides a simplified loading device in which a permanent magnet is arranged between a moving element and a fixed element for holding the moving element, a magnetic fluid is disposed in a gap developed at some midpoint in a magnetic circuit in which the magnetic flux of the permanent magnet passes through the moving element, and a shearing force of the magnetic fluid produced by the magnetic flux of the permanent magnet is exerted on the moving element as a loading force.
Also, the present invention provides a simplified loading device in which a permanent magnet is arranged between a rotating shaft and a fixed element for holding the rotating shaft, a magnetic fluid is disposed in a gap developed at some midpoint in a magnetic circuit in which the magnetic flux of the permanent magnet passes through the rotating shaft, and a shearing force of the magnetic fluid produced by the magnetic flux of the permanent magnet is exerted on the rotating shaft as a loading force.
In the present invention, the magnetic fluid is disposed on the peripheral surface of the rotating shaft or the inside surface of the fixed element.
Further, in the present invention, magnetic powder is dispersed in a solution as the magnetic fluid, a drag against shearing due to a fixed chain is created under a condition in which a fixed magnetic force is exerted, and a fixed drag is created even after shearing has been performed.